The most important subject in studies for improving the efficiency and characteristic of semiconductor devices is to reduce the crystal defect of a semiconductor layer grown on a substrate and to improve crystallinity of the semiconductor layer.
Various types of defects may be formed when fabricating an epitaxial wafer (hereinafter, these defects will be referred to as epitaxial defects). For instance, there may be presented various defects, such as a defect created in a basal plane of a lattice, a defect caused by the tilting of the lattice, and a defect created on a surface of the wafer. These defects may exert bad influence upon the semiconductor device employing the wafer. In addition, when the semiconductor device is fabricated by using the wafer, great leakage current may be generated due to the non-uniformity of metal electrode deposition and patterns.
A buffer layer is formed in order to reduce the dislocation defect during the crystal growth process. Thus, a mask forming process, a process for forming a pattern on a substrate through etching, and a regrowth process are additionally necessary to form the buffer layer.
Due to the above additional processes, the fabrication process is complicated, the fabrication cost is increased, and the quality of a substrate surface is deteriorated.